The ADAU1701's parameters can have 23 bits in their fractional parts, equivalent to approx. 6 decimal digits. Thus I suggest you have Matlab print your filter coefficients and gains, and enter them into your project, with a full six decimal places. Four places is plenty enough for typical parametric EQ filters, but your requirement appears to be a very sharp 8-pole filter with four high-Q sections. I'm not sure if the added resolution will help, but it's easy enough to try.

i'm sure this has to do with the spacing of the Frequencies being calculated by the Tool in simulation. Try slightly moving the center frequency and you will see that the peak happens at a completely different gain value. This doesn't mean that the gains are different, simply that the chosen (Simulation) points are not calculated at the exact frequency of interest.